


optimal genes

by crunchrapsupreme



Category: Shingeki no Kyojin | Attack on Titan
Genre: Alternate Universe - High School, Frottage, Love/Hate, M/M, Wall Sex
Language: English
Status: Completed
Published: 2014-03-13
Updated: 2014-03-13
Packaged: 2018-01-15 13:51:59
Rating: Mature
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 1
Words: 2,743
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/1307161
Author URL: https://archiveofourown.org/users/crunchrapsupreme/pseuds/crunchrapsupreme
Summary: <blockquote class="userstuff">
              <p>Jean and Eren have had a fueled rivalry since before they can remember, and when they get paired together for their mid-term project in Biology, they both come to realize a few things about themselves - and each other - that they hadn't realized before.</p>
            </blockquote>





	optimal genes

**Author's Note:**

> for a prompt someone gave me on tumblr about eren and jean being project partners and hating each other, getting into a fist fight, but then kissing on accident and thinking 'hey that was actually really awesome' and then sex \o/
> 
> also available to read on [my tumblr](http://crunchrapsupreme.tumblr.com/post/79440957232/optimal-genes-eren-jean-highschool-au) !

Their rivalry is amusing to practically everyone, including all of their teachers, and Jean’s almost 100% sure that that’s the reason why him and Eren get paired together for their mid term project in Biology. It was supposedly ‘random’, but with the way Mr. Smith glances at Jean out of the corner of his eye as he’s passing out the rubric, Jean _knows_ he put them together on purpose.

As Jean reads the guidelines, he lets out a slow breath, willing himself not to glance at the boy two rows over and three seats back. The boy he’s going to have to work rather closely with in the next few weeks. The boy he’s going to have to meet up with _outside of school hours_.

He doesn’t notice the bell ringing until a smack on his desk makes him jump and glance up, coming face to face with Eren fucking Jaeger.

“Here’s my address. Come over this weekend so we can get started and finish this stupid thing as soon as fucking possible.”

Jean glances down to see a piece of ripped notebook paper with an address scrawled hastily between the lines. When he looks up Eren’s already halfway to the door, and Jean suddenly feels a rush of annoyance.

“Why the hell do we have to meet at _your_ house? Why can’t we meet at mine?”

Eren spins around and glares, shoving his hands in his pockets and raising an eyebrow menacingly. Jean stands up from his desk, stalking a bit closer because he’s always blessed the based gods that he has a good few inches on Jaeger, so looking down on him is a perfect intimidation method. Although Eren is pretty good at standing his ground, Jean still gets satisfaction in watching the shorter teen have to crane his neck up to look Jean in the eye.

“ _Because_ ,” Eren continues, voice strained with impatience. “I’m allergic to cats you fucking _dumb ass_.”

Jean blinks, briefly recalling his three cats, and he almost feels bad. Almost. But then Eren’s rolling his eyes as if Jean’s the most idiotic person he’s ever encountered, and then he’s walking away, hiking his backpack higher on his shoulder and leaving Jean grumbling angrily to himself as he stuffs the piece of notebook paper in his pocket and makes his way to the cafeteria for lunch.

\--

On Saturday, Jean punches Eren’s address into his phone and finds out it’s only about a 20 minute walk from his own house, and the March weather is pleasantly chilly but not too bad, so Jean throws on a hoodie and decides to walk. He’s briefly concerned because Eren never gave him a specific time to come over, but he decides not to worry about it too much. It’s not his fault Eren gave him the most vague fucking instructions ever.

His Biology textbook is heavy in his backpack, and Jean can’t stifle the sigh of relief as he finally makes it to his destination, his phone beeping in completion as he walks up the driveway and to the front door. It’s homey, with a few freshly planted flowers in ceramic pots on the porch, and Jean eyes them as he knocks loudly, averting his eyes as he takes in the ‘Welcome’ mat beneath his feet.

The door swings open after a few moments, and Eren blinks at him emotionlessly. Jean shifts uncomfortably.

“Come on,” Eren says, turning around and walking back in the house. Jean follows a little hesitantly, because this feels _strange_. He never thought he would ever be inside Eren Jaeger’s _house_. It feels oddly intimate, because this is where the other teen lives. This is where he sleeps and watches television and eats dinner and showers and does his homework. It feels like Jean is stepping into a part of Eren’s life he was never meant to step into, because he’s never had an interest in deducing that hey, Eren’s an _actual human being_ and not just a complete dumbass put on earth to test Jean’s anger issues.

He follows Eren upstairs, trying not to actually take in the house and it’s stark, forest green wall paper and scratchy-soft beige carpeting. When they get to Eren’s room, Jean almost doesn’t want to walk inside, but Eren glances at him briefly and Jean glares, shuffling inside and tossing his backpack on the floor before doing the same himself, sitting cross legged next to Eren’s bed (navy blue comforter, disheveled and unmade) and unzipping his bag in silence.

Eren snorts softly. “Always this polite in a guest’s home?”

Jean ignores him and pulls out his Bio book and a few notes he had taken the night before. “Let’s just get this over with.”

Eren plops down on his bed, rolling on his stomach and propping his head up with his hands as he watches Jean spread out the supplies he brought for their cell model.

“Styrofoam? Really?” Eren points out, raising an eyebrow as he watches Jean set down the white styrofoam sphere. “You do realize every other sophomore in highschool is going to be using the exact same material. Where’s your originality, Kirchstein?”

“Fuck off,” Jean mutters, because yeah, he _had_ thought about the fact that styrofoam is wholly unoriginal, but it’s _easy_ , and Jean is pretty artistically challenged. Fuck ‘originality’. He just wants to get this stupid thing finished with so he can go back to pretending he never saw the inside of Eren Jaeger’s bedroom.

Eren just rolls his eyes again before reaching over to his desk and grabbing his own notes. “Alright, whatever. Let’s just do this.”

\--

“Did you get hit on the head when you were younger? Did you snort too many paint fumes? Eat too much cheap off-brand macaroni and cheese or something?” Eren asks, shaking his head and laughing bitterly. “Jesus _fuck_ , that’s not what a mitochondria looks like, idiot.”

Jean grinds his teeth together and flings his notes at Eren, but the paper just flutters back to the floor. “Fine, how about _you_ sculpt the fucking mitochondria out of goddamned construction paper then!”

“I can’t. I have no artistic talent whatsoever,” Eren says, and he sounds almost _happy_ about the fact, smirking and tilting his head to the side, eyeing Jean’s pathetic half-finished construction paper mitochondria.

“God, shut the fuck _up_. If you’re not going to help, then don’t criticize _my_ contribution to this shitty project.”

“I’m helping!” Eren protests, glaring daggers at the boy sitting on his floor. Jean ignore him, going back to taping together his pathetic cell structure, and Eren sits up on the bed. “Hey, fucker, don’t _ignore me.”_

Jean doesn’t have time to react much before a hand is reaching out, snatching his sculpture and crushing it in a tanned fist. Eren lets the ruined piece of work flutter to the carpet in front of Jean, and the taller boy blinks before the room goes silent.

“Are you fucking _serious_ \- ” Jean starts, but cuts himself short before whipping his eyes up, and Eren blinks at him innocently, and shit, if Satan were a reincarnate himself, Jean’s pretty sure his human name would be Eren fucking Jaeger.

Eren’s lips twitch on a smirk, and Jean’s pretty sure his own body temperature has risen above boiling, the controlled anger inside of him now bubbling over and he doesn’t even think twice as he swings a fist, socking Eren in the jaw. His form was off, and he didn’t pull back enough to do any real damage unfortunately, but Eren tumbles off his bed in surprise, and before Jean can really land another blow, a body is tackling into his own and knocking them both to the floor.

“You fucking - !” Eren manages, kneeing Jean in the stomach, but one thing Eren never had much of was body strength, so Jean easily rolls them both over, straddling Eren’s narrow waist and holding the boy down by his wrists.

Eren eventually stops struggling once he realizes he’s stuck under Jean’s weight, and he eventually slumps in defeat, face flushed from his squirming and hands still balled into fists.

Jean glares down at him, panting quietly, and says, “Are you _always_ this much of an asshole?”

“It’s not my fault you don’t know what the fuck a mitochondria looks like.”

“Fuck _off.”_

“Fuck _you_.”

“No, just. Fuck. _Fuck_ , I can’t fucking _stand you_ ,” Jean blurts out, face burning with anger and confusion because Eren’s wiggling beneath him again and the boy’s hair is disheveled against the carpet and his flushed cheeks are making his faint dusting of freckles stand out, and Jean leans down closer, eyes locked with shining green eyes brimmed with fire, and when Eren cranes his head up a moment later, pressing their mouths together, Jean almost forgets what’s happening.

His grip goes slack on Eren’s wrist, but the boy keeps his arms up, tilting his head to the side and biting down on Jean’s bottom lip. The pain shocks him back into reality, and Jean gasps and scrambles off of Eren quickly, his body already missing the warmth between his thighs but his mind already screaming at him in confusion, because _what the fuck is happening?!_

“What - ”

“Fuck you,” Eren hisses, sitting up and wiping the back of his mouth, but there’s not as much venom in the words as usual, and if Jean isn’t mistaken, there’s a hint of fear in his eyes, timid and unmistakable. Jean wonders if he looks the same.

Eren glares at him again, but then slowly scoots closer and grabs his notes again, silently going back to work, and Jean wants to make a retort about him actually _doing some work_ , but he can’t bring himself to voice the words, his throat dry and his lips tingling, and when Eren darts a tongue out to wet his own lips, Jean tries not to follow the swipe of his tongue.

\--

They work mostly in silence, and without the bickering and arguing and meaningless insults, about four hours later they have a finished project sitting in between them on the floor. It’s a solid B+ of work, and Jean’s perfectly okay with a B+. Shit, a B+ is fucking _fantastic_.

“So. I guess we’re, uh. Done,” Jean gets out, scratching the back of his neck, because even though his mind was solely concentrated on Plant Cells for the past few hours, he couldn’t push down the strange desire of needing to kiss Eren again. It was…. it was _nice_. Eren’s lips were soft and he was warm and pliant against him, and even though it ended quicker than Jean can remember, there’s _no way_ he can forget.

“Yep,” Eren answers curtly, standing up and straightening out his shirt. He’s been the quietest of the two the past few hours, oddly skittish, and Jean hates him, he _hates him_ , and he’s never going to have to step foot in his room again because the project is done, and he’s never going to have to meet with Eren after school again because they have no reason to, and Jean hates him _so fucking much_ -

Eren gasps loudly when Jean presses him against the closed door suddenly, hands fisted in the front of Eren’s tee shirt, and the shorter boy swallows before glaring half halfheartedly.

“What the _fuck_ are you - ”

“Why did you kiss me?”

Eren blanches, and Jean’s never seen him looking so vulnerable before. He’s so used to seeing this kid so full of himself, head held high, sure of his actions, sure of his presence. It’s strange seeing him so out of himself. It’s making him look even smaller than he usually is, and Jean leans in closer, because Eren has nowhere to go and Jean can’t stop staring at his mouth.

“What the _hell_ are you talking about - ”

“No, fuck _you_ ,” Jean hisses, and then he kissing Eren, sliding a hand up to cup his jaw, sharp and smooth beneath the palm of his hand, and Eren tilts his head into the touch once he finally relaxes and kisses back.

This time, Jean is fully conscious of what’s happening, and there’s no pulling back, so he lets himself press closer, the lines of their bodies connecting, and when Eren hesitantly wraps his arms around Jean’s neck, the taller boy hums in encouragement.

“Fuck,” Eren manages once they pull apart for air. “I _hate_ you. Why the fuck - ”

“I don’t know,” Jean replies, breathless, and he ducks his head to mouth at Eren’s neck. “I don’t know and I don’t really care, either. So just _shut up_ for once, okay?”

It’s quiet, but then a quiet, breathy little, “ _okay_ ,” jump starts Jean’s nerves, and he reaches down to grip Eren’s thighs, hiking the shorter teen up until he’s forced to wrap his legs around Jean’s waist, ankles crossing in the back.

“You better not drop me,” Eren hisses, craning his neck back as Jean sucks at his adam’s apple.

“M’not gonna drop you. You’re tiny.”

“Fuck you, I’m not _tiny_ ,” Eren growls, digging his nails into Jean’s shoulders. Jean snorts out a quiet laugh, pulling back to look Eren in the eye.

“You kind of are,” he says, but then smirks as he spots the blush coloring Eren’s cheeks. “But it’s okay. It’s cute.”

Eren’s glare could set fires, but the blush creeping down his neck dilutes the intimidation of it. “Fuck. You.”

Jean chuckles, but then he’s rolling his hips up, pressing their arousals together, and a gasp is ripping from Eren’s throat, a broken, “ _oh_ ,” escaping his lips, and Jean decides he really likes the sound of that. He lets a hand creep up the back of Eren’s shirt, feeling warm skin and taunt muscles, and he creeps his fingers up until he can scratch back down, nails digging in just shy of breaking the skin. It’s a slightly awkward angle, but when Eren makes a choked noise, arching his back into a gorgeous curve, Jean decides it was _so_ worth it.

Eren grips Jean’s hair, presses their foreheads together, says, “M’gonna…  _fuck_ , I’m - ”

“ _C’mon_ ,” Jean mumbles in reply, wrapping Eren up tighter in his arms as he rocks his hips up quickly and unevenly, and Eren squeezes his eyes shut as he finally releases in his sweat pants, his whole body tensing up briefly before going slack in Jean’s grip. It only takes a few more rolls of his hips for Jean to follow suit, and he comes with a quiet groan, muffled against Eren’s cheek, and he shivers when the shorter boy scratches through the hairs at the nape of his neck lazily.

Jean carefully lets Eren slide back onto his feet, slightly shaky, and Jean steadies him with a hand on his hip. Eren flinches, but soon relaxes into the touch as a flush colors his face again, and _jesus_ , Jean didn’t know this boy could blush so much. He’s so used to only seeing the redness in his face from anger or frustration, never from embarrassment or pleasure. It’s oddly satisfying.

“I think…..” Eren starts, clearing his throat and glaring slightly at the ground. “I think we could use some finishing touches on our project. Um. It’s. I don’t think it’s done.”

Jean raises an eyebrow, says, “You don’t?”

Eren shakes his head and crosses his arms, clearing his throat. “You should come back tomorrow. So we can finish it.”

Jean’s lips twitch as he reaches down to pack up his stuff, and when he stands back up, slinging his backpack over his shoulder, Eren is sitting on the bed, glaring at him, but there’s no anger in the stare, only confusion and, if Jean isn’t mistaken, _hope_.

He lets himself smile, just the tiniest bit, and Eren’s own lips twitch in response, and Jean decides it’s much nicer than all of those douchey smirks and empty, angry grins he’s been presented with before. This smile is small, but it’s genuine, and when Jean walks over, leans down to places a chaste kiss on Eren’s cheek just to see the boy blush again, he wonders why he ever became such fierce enemies with him in the first place.

Because, although it’s always refreshing to let out his anger through fists and shoves, Jean has a feeling he just discovered a new way to let out his pent up frustrations, because Eren’s orgasm face is probably more relaxing than any punch to a face could ever hope to be.  


End file.
